Basement Leaks - Typical Sources

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Having conducted thousands of basement/foundation inspections over the years, we have concluded that approximately 90% - 95% of the causes of a damp, wet basement are attributable to one or two of the "usual suspects" as illustrated below.

Caution: There are many ways by which water can enter your basement; it follows that the repair method chosen must address the problem encountered. Without visual confirmation of the actual problem, or without absolute confirmation of the source of the leak using diagnostic equipment, many homeowners pay for basement waterproofing work far in excess of what is actually required, including waterproofing work performed in the wrong location, or basement leak repair work that is not needed because the source of the basement leak is not attributable to the foundation.

From the images below it is clear that basement leaks are relatively easy to identify when the foundation wall is exposed. If a contractor does not show you undeniable evidence of the source of your basement leak there is a real risk that you will waste your money and/or not address the real source of the water in your basement.

water entering through cracks basement leaks poured concrete foundations How water leaks through a concrete block foundation How water enters a cold cellar

Visible Mold

In a residential setting, basement leaks typically leave stains on the foundation walls. When your basement is finished, many basement leaks remain hidden; however, mold on drywall, baseboard discoloration and wet carpets are often the first indication that there is a leak in the basement. Here is what you can expect to see when your basement is finished:

Mold growth on drywall in the basement Mold on drywall behind wainscotting Mold of various colours growing on drywall in the basement

Here is what you can expect to see when the bare foundation walls are exposed:

Foundation Cracks

Foundation crack with visible sediment Foundation crack with visible sediment and mineral deposits Wet crack with mineral deposits

Leaking tie-rod holes

Water leaking through tie-rod hole Tie-rod holes with evidence of significant leakage Actively leaking tie-rod hole

Corroded snap rods

Snap rod with evidence of corrosion

A hole through the foundation wall accommodating a conduit to the electrical panel or a conduit for air conditioning lines

Electrical conduit passing through the foundation wall above grade Electrical conduit visible from interior

Honeycombing

Honeycombing between 2 tie-rod holes Large area of honeycombing with evidence of sediment

Water leaking from the top of the foundation

Leak from top of foundation

Water leaking from an I-beam pocket

I beam pocket leak

Water leaking from the top of the cold cellar walls

How water typically enters a cold cellar

Water coming in between the basement window frame and the top of the foundation, or through the window itself

Evidence that water leaked between the window frame and the top of the wall Evidence of inadequate window well drainage Evidence of window well drain failure and sediment contamination

Concrete block foundation wall leakage

How water leaks through a concrete block foundation Saturated concrete block with water gushing from weeping hole Wet concrete block wall corner

Concrete block wall with significant evidence of water leakage

Condensation on the foundation wall dripping down the wall from behind the insulation.

This is typically seen in homes less than 5 years old.

Less frequent sources of basement leaks

On occasion, water will originate from one or more of the following sources:

  1. Plumbing leaks
  2. Water leaking from inside the fireplace chimney
  3. Water leaking from the roof to the basement behind the walls along the wood framing. This typically results from detached roof flashing around the chimney or from water backing up from clogged or ice-filled eavestroughs
    Rain water that gets behind the flashing around the chimney can find it's way into your basement
  4. Condensation dripping from very cold ducting or very cold water pipes in a high humidity environment
  5. An overflowing liner of an inoperative sump pump
  6. Water coming into the basement from beneath the floor slab
    Water beneath the basement floor from a high water table could be the root cause of a basement leak Water beneath the basement floor can introduce significant water into the basement
  7. Water entering the basement from the floor drain due to back pressure from the storm sewer on the street
  8. Water leaking from a chimney cleanout
    Rain water is entering the chimney on the roof and draining down the chimney to the cleanout

Homeowner Tip: Given the many potential sources of a leaking basement it is clearly necessary to positively identify the source of a leak in order to determine which type of repair is required. A truly professional waterproofing contractor will spend the necessary time to locate the source of the leak and explain how the proposed repair solution is best from both technical and cost perspectives; our Basement Waterproofing Repair Methods page provides a table detailing the available professional foundation repair methods for the correction of wet basement issues. Unfortunately, we have met many unhappy homeowners who either paid far more than was necessary to fix a basement leak or who have had their foundations excavated only to discover, thousands of dollars later, that the actual cause of the leak was not properly identified and therefore, not addressed.

If a waterproofing contractor has not conclusively proven to you how water has entered your basement, and then suggests that external excavation and waterproofing will correct the problem, we suggest that you hire a more professional company.

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